4TPI Tap in 5/8 inch in ACME

[timber]

I am after a 5/8 inch 4tpi tap.ACME

It is to be used to cut a thread into some Delrin. Need to make a new half-nut for a Legacy wood lathe. At a push a short bit of leadscrew would do.I could shape it up to cut the thread.
If you have such a thing to sell let me know
Timber

 

[bugbear]

I am after a 5/8 inch 4tpi tap.ACME

It is to be used to cut a thread into some Delrin. Need to make a new half-nut for a Legacy wood lathe. At a push a short bit of leadscrew would do.I could shape it up to cut the thread.
If you have such a thing to sell let me know
Timber

I don't think such taps are made, since the cutting forces would be extremely high.

EDIT; I'm wrong; some Acme taps are made;

http://www.tracytools.com/taps-and-dies/acme-taps

A screwcutting metal lathe owner may be able to cut you a new half nut though.

BugBear

 

[marcros]

Have you seen this http://bbs.homeshopmachinist.net/thread ... 554d9404eb

may or may not be relevant to your need.

 

[timber]

Have you seen this http://bbs.homeshopmachinist.net/thread ... 554d9404eb

may or may not be relevant to your need.

Thanks marcros, I will have to try that, a great help

bugbear
Thanks but I could not see a 4tpi acme

 

[Retire2004]

Hi Timber, 4TPI on a 5/8" dia. sounds a very course thread! It could actually be an 8TPI two-start thread. How far does the carriage move for 1 turn of the leadscrew? What is the distance from one thread form to the next? (1/4" or 1/8") Is the thread RH or LH.
Regards, Tudor

 

[timber]

Hi Timber, 4TPI on a 5/8" dia. sounds a very course thread! It could actually be an 8TPI two-start thread. How far does the carriage move for 1 turn of the leadscrew? What is the distance from one thread form to the next? (1/4" or 1/8") Is the thread RH or LH.
Regards, Tudor

Hi Tudor
It is from the USA
It is a right hand thread and one turn moves the carriage 1/4 inch ----It is not a two start thread
Regards
Timber

 

[Retire2004]

Hi Timber, Thanks for the info. Could be a "stub" Acme thread, this is a lower profile used when a stronger root dia is required. For a 4 TPI this would have a basic thread depth of 0.075" pitch instead of 0.125" on a Standard Acme. As already stated, a normal 5/8 dia would have a min of 8 TPI. Maybe Legacy make it a non-standard in order to justify crazy prices for spares!
Tudor

 

[bugbear]

Have you seen this http://bbs.homeshopmachinist.net/thread ... 554d9404eb

may or may not be relevant to your need.

Thanks marcros, I will have to try that, a great help

bugbear
Thanks but I could not see a 4tpi acme

Hence my use of the word "some"

BugBear

 

[timber]

Hi Timber, Thanks for the info. Could be a "stub" Acme thread, this is a lower profile used when a stronger root dia is required. For a 4 TPI this would have a basic thread depth of 0.075" pitch instead of 0.125" on a Standard Acme. As already stated, a normal 5/8 dia would have a min of 8 TPI. Maybe Legacy make it a non-standard in order to justify crazy prices for spares!
Tudor

Hi Tudor
The depth is around the .090 mark
I agree I am sure it a closed shop ,have to buy from them.
they don't seem to answer emails or respond to most questions asked by other owners of Legacy lathes.
I did think about cutting a short length of the leadscrew to make a tap. I don't seem to use the full length of 6 foot
Timber

 

[chaoticbob]

Hi Timber. Just looked at the thread chart on my lathe - it does 4TPI. If all else fails, I'd be happy to have a go at this for you. I've made custom metric taps before, but never had to cut an ACME tap, so cost to you would be material and postage - what I'd get out of it would be some new experience.
Rob.

 

[bugbear]

Hi Timber. Just looked at the thread chart on my lathe - it does 4TPI.

Many lathes have 8 TPI leadscrews, so it's not a complex change wheel calculation.

It might be easier to cut the required half-nut than make a hard-to-use tap to cut the half-cut.

BugBear

 

[timber]

Hi Timber. Just looked at the thread chart on my lathe - it does 4TPI. If all else fails, I'd be happy to have a go at this for you. I've made custom metric taps before, but never had to cut an ACME tap, so cost to you would be material and postage - what I'd get out of it would be some new experience.
Rob.

Hi Rob
I have just sent you a P.M.
Rich